McDonald's E. coli outbreak hit 14 states — quick response could not undo damage

In September and October 2024, an E. coli O157:H7 outbreak was traced to slivered onions used on McDonald’s Quarter Pounder hamburgers. The outbreak affected 104 confirmed cases across 14 U.S. states, causing 34 hospitalizations and one death. The contaminated onions were supplied by Taylor Farms, a produce supplier based in California.

McDonald’s responded within days of the CDC alert. On 22 October 2024, the company voluntarily removed the Quarter Pounder from menus in the affected states and stopped serving the slivered onions and beef patties (the patties were later cleared as a source). The fast response was praised by food safety experts as appropriate and responsible. However, the damage to McDonald’s brand was immediate: same-store sales in the US fell during the quarter, and the company’s stock dropped 5% in the days following the announcement.

The incident highlighted a structural vulnerability: McDonald’s supply chain was large and diversified, but a single ingredient — slivered onions from one supplier — was enough to disrupt menus across 14 states. The company spent millions on advertising to reassure customers and eventually restored the Quarter Pounder with onions from a different supplier. The Taylor Farms facility implicated in the outbreak was permanently closed. McDonald’s reported that the financial impact of the outbreak was material enough to affect its quarterly earnings guidance.